Steam adds community-powered reviews that can be rated using a simple thumbs up/down system instead of a numbered system.
Source:
Valve Press Release
Steam Family Library Sharing is released allowing players who share a computer to also their their libraries with each other.
Source:
Valve Press Release
Steam Launches In-Home Streaming. Users who have two computers on the same network automatically connect and allow you to remotely play and install games as if you were using the remote computer.
Source:
Valve Press Release
Valve casually releases Source 2 and new developer tools complete with a new version of Hammer, model editor, and material editor with the Dota 2 workshop.
Source:
LambdaGeneration
Valve adds game broadcast streaming to natively to the Steam platform.
Source:
Valve Press Release
2015
In the third month of the year on the third day at 3:00PM, Valve formally announces Source 2, SteamVR hardware, and Steam Link streaming box at GDC 2015.
Source:
Valve Press Release